The present invention relates to a thermal transfer recording medium usable in a high-temperature environment.
A thermal transfer recording medium is used for producing printed images in such a manner wherein the heat-meltable ink layer thereof is selectively heated with a heating device such as a thermal head to melt-transfer heated portions of the ink layer onto a receptor. The thermal transfer recording medium has widely been used in printing devices for word processer, personal computer, etc. There is a possibility that the thermal transfer recording medium is used in a high-temperature environment wherein the temperature rises to 60.degree. C. or higher, such as the tropics.
However, a conventional thermal transfer recording medium is unusable in such a high-temperature environment.
The conventional thermal transfer recording medium includes a wax-type one wherein the vehicle of the heat-meltable ink layer is composed mainly of a wax, and a resin-type one wherein the vehicle of the heat-meltable ink layer is composed of a wax and a resin in combination.
Generally most waxes have a melting point of about 60.degree. to 80.degree. C. Therefore, the wax-type thermal transfer recording medium is apt to be unusable in the above-mentioned high-temperature environment because the ink layer assumes a softened or flowing state during transportation, storage or use.
In the case of the resin-type thermal transfer recording medium, the ink layer per se does not cause any problem because the ink layer has a high melting or softening point. However, when the ink layer is provided directly on the foundation, the ink layer exhibits great adhesion to the foundation when transferring, resulting in a poor transferability. For that reason, the resin-type thermal transfer recording medium generally requires a release layer between the foundation and the ink layer. The release layer is generally composed mainly of a wax, which makes the resin-type medium unusable in the high-temperature environment.
In view of the foregoing, it is an object of the present invention to provide a thermal transfer recording medium which is usable in a high-temperature environment.
This and other objects of the present invention will become apparent from the description hereinafter.